DETROIT -- Three people are dead and many others injured after a horrific multiple-vehicle accident scene that stretches for more than a mile on I-75 southbound in Detroit, police said.

Michigan State Police Lt. Michael Shaw said two step siblings from Windsor, ages 9 and 7, were killed. Their parents and 10-year-old sister were all in critical condition at area hospitals, Shaw said. South of that accident, a 54-year-old Allen Park man died in another crash.

According to State Police, I-75 southbound was reopened at about 4 p.m. EST.

Motorists described total white-out conditions as they approached Springwells around 9:30 a.m. Motorists said they slammed on their brakes, but slid on slick, snow covered roads.

MDOT spokesman Rob Morosi said sudden snow squalls whipped across the freeway just after 9 a.m., and although road crews had pre-salted the expressway's lanes, snowfall quickly turned to ice on the I-75 bridge over the Rouge River. The accident started on the bridge, according to MDOT.

At least a dozen fire and emergency vehicles responded to the scene, and at least 10 flatbed trucks came to assist.

According to a first responder on the scene, one victim's car is shattered with the back of the car folded up over the front of the car.

Detroit EMS Chief Jerald James said a dozen people, not including those killed, were transported to area hospitals with injuries, including broken bones, head trauma and lacerations. He said Detroit had four ambulances and a rapid response unit on the scene and about five private ambulance companies sent four or five units each, as well.

He said 30-plus people were also treated for injuries at the scene.

Shaw said some of those transported were badly injured.

Three victims were transported to Oakwood Hospital in Dearborn by ambulance, said Dr. John Fath, the trauma medical director at Oakwood Healthcare

All are in stable condition and should be released within hours or days, he said. The victims suffered blunt trauma from a motor vehicle collision, said Fath. He could not supply additional details. The patients arrived roughly an hour after the hospital was alerted that it would receive as many as 15 patients from the accident. Fath said he was unsure whether the hospital will get additional patients.

Shaw said police were investigating between eight and 10 crashes within the accident scene. He said between 150 and 200 vehicles were either involved in crashes or were blocked by accidents.

Some of the vehicles at the scene are totaled, others have minor damage, one appeared to be wedged under a fuel truck and some ran into the embankment.

Northbound I-75 in the same area has been reopened.

According to MSP, southbound I-75 will be closed for at least four hours, and possibly through the evening rush hour. Emergency personnel were focused, as of just before noon today, on rescuing injured motorists.

Tow trucks are on site waiting to remove less damaged vehicles, while others were being pushed from the road by heavy machinery. As well, the Wayne County Medical Examiner's office was on scene at about 2:30 p.m. to remove the body of a victim.

The Michigan State Police set up a mobile command post to begin coordinating how to remove crashed vehicles and handle hazardous materials removal because several crash-related fuel spills were reported.

The Detroit Fire Department was on scene dealing with spilled diesel fuel.